| Low loss photonic waveguide having high index contrast glass layers -> Monitor Keywords |
|
|
  Low loss photonic waveguide having high index contrast glass layersUSPTO Application #: 20080050076Title: Low loss photonic waveguide having high index contrast glass layers Abstract: A low-loss photonic waveguide in the form of a Bragg optical fiber is provided that includes a dielectric core region extending along a waveguide axis that is characterized by a low amount of Rayleigh scattering, and a dielectric confinement region surrounding the dielectric core region that includes alternating layers of different glass compositions having relative refractive index differences that are at least 0.10, and preferably at least 0.30. The core region may be formed from air. The confinement region includes alternating high and low index glass layers wherein the high index layers are substantially pure silica mixed with index raising dopants that form enough % of the high index glass layers by weight to achieve the aforementioned 0.10 difference in indices of refraction, while the low index glass layers may be either substantially pure silica, or silica mixed with index lowering dopants to increase the index contrast between the layers. The use of alternating high and low index glass layers to form the dielectric confinement region allows the Bragg fiber to be usually manufactured on a large scale via conventional fiber optic fabricating techniques with relatively few steps. The resulting fiber is capable of conducting high photonic power levels, and is particularly compatible with short photonic wavelengths, such as ultraviolet light. (end of abstract)
Agent: Corning Incorporated - Corning, NY, US Inventors: Ming-Jun Li, Daniel Aloysius Nolan, Carlton Maurice Truesdale, James Andrew West USPTO Applicaton #: 20080050076 - Class: 385125 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080050076. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]1. Field of the Invention [0002]This invention generally relates to photonic crystal waveguides, and is specifically concerned with a Bragg optical fiber waveguides having a dielectric confinement region formed from alternating layers of glass having high-contrast optical indices. [0003]2. Description of the Related Art [0004]Optical waveguides in the form of optical fibers are well known in the prior art, and are used to transmit optical signal information between remote locations. The most common type of optical fiber includes a doped silica core region extending along its central axis surrounded by an undoped silica cladding that has a refractive index less than that of the core region. Optical signals are confined along the core region via total internal reflection (TIR) that results from the contrast in indices of refraction along the core-cladding interface. Almost all such index-guided optical fibers are silica-based in which one or both of the core and cladding are doped with index-raising or lowering dopants to produce the necessary index contrast at the core-cladding interface [0005]While such index-guided optical fibers work reasonably well for their intended purpose, some amount of optical scattering occurs at a microscopic level between the dopant-containing glass composition that forms the light-conducting core, and the pulses of laser light that form the optical signal. Such scattering is known as Rayleigh scattering, and results in greater signal attenuation the farther the distance the optical signal travels through the core. In addition to signal attenuation, cores formed from doped silica also induce distortions in the shape of the optical signal as a result of optical non-linearities. Finally, the solid core of doped silica limits the amount of optical power that can be transmitted through the fiber due to damage of glass from high optical power, the damage being caused by the intrinsic absorption of the bulk glass through the formation of absorbing color centers, or from absorption due to contamination of the end facets. [0006]Bragg optical fibers, which operate as photonic crystal waveguides, are also known in the prior art. Such optical fibers include a core formed of air or some other low Rayleigh-scattering medium surrounded by multiple dielectric layers formed from optical materials having contrasting indices of refraction. The multiple layers form a cylindrical mirror that confines light to the core region over a range of frequencies. Hollow-core Bragg optical fibers offer a number of advantages over conventional, index-guided optical fibers including substantially less signal attenuation per unit distance of fiber due to vastly reduced amounts of Rayleigh scattering, and the ability to conduct substantially higher photonic power levels due to reduced interaction with the material in the hollow core region. Additionally, signal distortions caused by optical non-linearities are much lower than for standard, index-guided optical fibers, while the transmission speed may be up to 50% higher since light travels faster in a gas or vacuum than through a solid. A final advantage is the potential for improved bend performance because Bragg confinement is not as susceptible as total internal reflection is to degradation by bending. [0007]Unfortunately, there are a number of shortcomings associated with known Bragg optical fibers which have thus far prevented them from realizing their full theoretical potential. For example, in order for such a fiber to have a high bandwidth, high index contrast layers are needed to form the dielectric confinement region. In one such Bragg fiber, this was accomplished by forming the high index layers of tellurium having a refractive index of 4.6, and by forming the low index layers of a polymer having a refractive index of 1.59. However, because the tellurium and polymer layers are made by two different processes, this approach many requires fabrication steps and is not suitable for large scale manufacturing. Additionally, the polymer layers are less resistant to heat than glass layers, which renders the resulting fiber incompatible with the transmission of high photonic power levels. In another design of Bragg optical fiber, the high index contrast is accomplished by using layers of air between layers of high-index glass. However, such a design requires the use of very thin (around 45 nm) glass bridges which renders this particular type of Bragg optical fiber difficult to manufacture. [0008]Accordingly, there is a need for a Bragg optical fiber that preserves all of the low-loss, low distortion and high power transmission capabilities in a design that is relatively easy and inexpensive to manufacture. Ideally, such a Bragg optical fiber would have a dielectric confinement region formed from alternating layers of high-contrast glass compositions so that the resulting fiber could be easily manufactured by way of conventional optical fiber fabricating techniques. Additionally, it would be desirable if the glass composition material were relatively common and inexpensive to reduce the cost of fabrication. Finally, the index contrast between the layers forming the confinement region should be at least on the order of 0.10 so that a high bandwidth capability is achieved. SUMMARY OF THE INVENTION [0009]Generally speaking, the invention is a low loss photonic crystal waveguide comprising a Bragg fiber waveguide that overcomes the aforementioned short comings associated with the prior art. To this end, the Bragg fiber waveguide of the invention includes a dielectric core region extending along a waveguide axis that is characterized by very low Rayleigh scattering, and a dielectric confinement region surrounding the dielectric core region that includes alternating layers of different glass compositions having relative refractive indices that differ by at least about 0.10, and preferably by about 0.10 to 1.00. Preferably, the dielectric core region is devoid of solid material and is filled with a gas such as air in order to minimize Rayleigh scattering. Alternatively, the dielectric core region may be formed from a vacuum, or a low loss solid material such as pure silica without dopants. However, air is preferred due to the very low scattering losses and the ease of manufacture. [0010]The dielectric confinement region includes alternating high and low index glass layers, wherein the high index layers are preferably substantially pure silica mixed with index raising dopants that form at least 10% of the high index glass layers by weight. The low index glass layers may be formed from either substantially pure silica without any dopants, or substantially pure silica mixed with index lowering dopants in order to increase the contrast of the indices of refraction between the alternating glass layers. When an index lowering dopant is used in the low index layers, the proportion mixed with the silica is preferably chosen such that the viscosity of the molten glass forming the low index layers is substantially the same as the viscosity of the glass forming the high index layers in order to reduce thermal stresses between the layers during manufacturing. [0011]The high index layers within the dielectric confinement region may include index raising dopants such as TiO.sub.2, GeO.sub.2, Al.sub.2O.sub.3, ZrO.sub.2 and Nb.sub.2O.sub.5. The low index layers may include index lowering dopants such as fluorine and B.sub.2O.sub.3. Preferably, the index raising or index lowering dopants added to the silica that forms both the high and the low index layers constitutes between about 10% and 30% of the resulting doped glass layers by weight, and the dielectric confinement region includes at least three or more pairs of alternating layers of high and low index glass. [0012]Because the Bragg fiber in the invention may be formed entirely of glass compositions, it may be easily manufactured by conventional optical fiber fabricating techniques on a large scale, and with relatively few steps. The resulting fiber is mechanically and thermally robust and requires no special considerations for handling or installation. Finally, the resulting fibers are particularly compatible with ultraviolet wavelengths which in turn increases the bandwidth capacity of the resulting fiber. BRIEF DESCRIPTION OF THE DRAWINGS [0013]FIG. 1 is an enlarged, cross sectional view of the Bragg optical fiber waveguide of the invention; [0014]FIG. 2 is a family of curves illustrating changes in the refractive index of glass compositions containing different proportions of germanium dioxide (GeO.sub.2) for different wavelengths of light; [0015]FIG. 3 illustrates the first step of the preferred method for manufacturing the Bragg optical fiber of the invention wherein a glass soot blank is formed over a glass tube; [0016]FIG. 4 illustrates the second step of the preferred method of manufacture, wherein the soot layers of different glass compositions that were vapor deposited over the glass tube are fused and consolidated in a furnace to form a glass blank; [0017]FIG. 5 illustrates the next step of the preferred method of manufacture, wherein the glass tube is etched out of the glass blank to form a hollow core region; [0018]FIG. 6 illustrates the fourth step of the preferred method of manufacture, wherein the glass blank produced in the previous step is reheated and drawn down into a narrower blank; [0019]FIG. 7 illustrates the next step of the method, wherein the additional layers of alternating high and low index compositions vapor are deposited on the drawn-down glass blank produced in the previous step to form a second glass soot blank; and [0020]FIG. 8 illustrates the final steps of the invention, wherein the resulting second, glass soot blank is heated in the furnace in order to fuse and consolidate the soot layers of different high and low index glass compositions around its exterior. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Continue reading... Full patent description for Low loss photonic waveguide having high index contrast glass layers Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Low loss photonic waveguide having high index contrast glass layers patent application. Patent Applications in related categories: 20080240663 - Ultra high numerical aperture optical fibers - Various embodiments described include optical fiber designs and fabrication processes for ultra high numerical aperture optical fibers (UHNAF) having a numerical aperture (NA) of about 1. Various embodiments of UHNAF may have an NA greater than about 0.7, greater than about 0.8, greater than about 0.9, or greater than about ... ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Low loss photonic waveguide having high index contrast glass layers or other areas of interest. ### Previous Patent Application: Multi-wavelength, multimode optical fibers Next Patent Application: Apparatus and methods using hollow-core fiber tapers Industry Class: Optical waveguides ### FreshPatents.com Support Thank you for viewing the Low loss photonic waveguide having high index contrast glass layers patent info. IP-related news and info Results in 6.54574 seconds Other interesting Feshpatents.com categories: Accenture , Agouron Pharmaceuticals , Amgen , AT&T , Bausch & Lomb , Callaway Golf |
||
